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Plasma electrolytic oxidation(PEO)is carried out on 6061 Al-alloys in a weak alkaline electrolyte containing NaOH,Na2SiO3 and NaCl.Centered on the correlation of composition and structure,analyses by means of X-ray diffration(XRD),scanning electron microscope(SEM)and energy dispersive spectrometry(EDS)are conducted on the specimens,which have been PEO-treated under hybrid voltages of different direct current(DC)values(140-280 V)with constant alternate current(AC)amplitude(200 V).Attention is paid to the composition,properties and growth mechanism of oxide layers formed with hybrid voltages.Moreover,the main effects of DC value are discussed.Ceramic layers with a double-layer structure which combines hard outer and soft inner layers are found to be consist ofα-Al2O3,γ-Al2O3 and mullite.With the DC values increasing,the growth of the ceramic layers tends to have increasingly obvious three-stage feature.
Plasma electrolytic oxidation (PEO) is carried out on 6061 Al-alloys in a weak alkaline electrolyte containing NaOH, Na2SiO3 and NaCl. Centered on the correlation of composition and structure, analyzes by means of X-ray diffration (XRD) (SEM) and energy dispersive spectrometry (EDS) are conducted on specimens that have been PEO-treated under hybrid voltages of different direct current (DC) values (140-280 V) with constant alternate current (AC) amplitude ). Attention is paid to the composition, properties and growth mechanism of oxide layers formed with hybrid voltages.Moreover, the main effects of DC values are discussed. Ceramic layers with a double-layer structure which combines hard outer and soft inner layers are found to be consist of [alpha] -Al2O3, [gamma] -Al2O3 and mullite. With the DC values increasing, the growth of the ceramic layers to have increasingly obvious three-stage feature.